1. Field of the Invention
The present invention relates to a method of writing data on an optical disc. More particularly, the present invention relates to a method of correcting write strategy data by reflecting the electrical characteristics of each of a plurality of optical disc drives, and an optical disc drive performing the method.
2. Description of the Related Art
To correctly write data on an optical disc, the optical disc manufacturer should be known. This is because the optimum conditions for writing data on the optical disc depend on the optical disc manufacturer, who records the optimum conditions on a portion of the optical disc tracks. Data describing the optimum conditions are referred to as write strategy data. Accordingly, an optical write device used to write data on optical discs stores optimum write strategy data for every type of optical disc and writes data on optical discs using the optimum write strategy data in conjunction with the optimum conditions on the optical disc. Optical disc types may include compact discs (CDs) and digital versatile discs (DVDs).
FIG. 1 illustrates a block diagram of a conventional optical disc drive 100 of an optical write device. Referring to FIG. 1, the optical disc drive 100 may include an encoder 130, a write strategy block 140, a memory 150, a laser diode drive integrated circuit (IC) 160, and an analog front end (AFE) 170. An optical disc 110 and a host 120 are also illustrated for convenience of explanation.
The encoder 130 may receive data to be written on an optical disc 110 from the host 120, e.g., a personal computer, may eight-to-fourteen modulate (EFM) the received data, and may output the EFM data (EFM signal). The write strategy block 140 may output two write enable signals WE1 and WE2 using the EFM data and write strategy data TD1, TD2 and TD3 of the optical disc 110, stored in the memory 150. The write strategy data TD1, TD2 and TD3 are time parameters used to generate the two write enable signals WE1 and WE2. While three write strategy data TD1, TD2 and TD3 are shown in FIG. 1, more than three write strategy data may be used to generate more than two write enable signals. The time parameters are information representing when the two write enable signals WE1 and WE2 may be shifted to a logic high level or a logic low level, thus representing the relationship between the EFM data and the two write enable signals WE1 and WE2. This will be explained with reference to FIG. 2. The laser diode drive IC 160 may control a laser diode (see FIG. 2) using two current sources DAC1 and DAC2 provided by the AFE 170, and the two write enable signals WE1 and WE2.
FIG. 2 illustrates the relationship between the write strategy block 140, the laser diode drive IC 160 and a laser diode 210. The write strategy block 140 may generate the two write enable signals WE1 and WE2 using the signal EFM having information representing that effective data exists for a time 4T and the write strategy data TD1, TD2 and TD3 received from the memory 150. Here, T corresponds to one cycle of a system clock signal, and the time 4T is arbitrarily selected for convenience of explanation.
The first write enable signal WE1 may be generated using two write strategy data TD1 and TD2. The first write strategy data TD1 may correspond to a time period after the EFM signal is enabled, i.e., when the EFM signal goes from a logic low level to a logic high level. The second write strategy data TD2 may correspond to a time after the start of the fourth period of the time 4T in which the effective data of the EFM signal is disabled, but before the EFM signal is disabled. That is, the first write enable signal WE1 may go from a logic low level to a logic high level after the first write strategy data TD1, and may go from a logic high level to a logic low level after the second write strategy data TD2.
The second write enable signal WE2 may be enabled while the first write enable signal WE1 is enabled, i.e., while the first write enable signal WE1 maintains a logic high level. The third write strategy data TD3 may correspond to a time period during which the second write enable signal WE2 is enabled. While FIG. 2 shows that the enabled period of the second write enable signal WE2 corresponds to the front part of the enabled period of the first write enable signal WE1, the positions of the enabled periods of the first and second write enable signals may be changed using different write strategy data.
The laser diode drive IC 160 may include a first switch SW1, a first resistor R1, a second switch SW2 and a second resistor R2. The first switch SW1 may provide a current supplied from the first current source DAC1 to a first terminal of the first resistor R1 in response to the first write enable signal WE1. The first resistor R1 damps the current supplied from the first current source DAC1, and may provide the damped current to the laser diode 210, which is connected to a second terminal of the first resistor. The second switch SW2 may provide a current supplied from the second current source DAC2 to a first terminal of the second resistor R2 in response to the second write enable signal WE2. The second resistor R2 damps the current supplied from the second current source DAC2, and may provide the damped current to the laser diode 210, which is connected to a second terminal of the second resistor. However, the first and second resistors R1 and R2 may be omitted from the laser diode drive IC 160, such that outputs of the current sources are not damped.
In a period during which the first and second write enable signals WE1 and WE2 are simultaneously enabled, the laser diode 210 may be over-driven. Thus, the length and/or width of pits generated on the optical disc may vary, resulting in jitter.
As described above, even if write strategy data of every kind of optical disc manufactured by different manufacturers is stored, appropriately selected and used, not all problems that may arise when writing on an optical disc are solved.
The plurality of functional blocks 130, 140, 150, 160 and 170 shown in FIG. 1 may be part of a semiconductor device manufactured in a single chip or a system on chip (SOC). When semiconductor devices are mass-produced, they may have different electrical characteristics even when they are manufactured according the same specification. Furthermore, even if semiconductor device chips are produced from the same wafer, they may have electrical characteristics, even though they are considered normal if they conform to a particular specification.
For at least the above and other reasons, the same mass-produced optical disc drives may have different specifications. Accordingly, even when the same write strategy data is applied to optical discs manufactured by the same manufacturer, there may be differences between pits recorded on the optical discs due to the different specifications of the optical disc drives. This is because write strategy data is applied to optical discs without considering different specifications of individual optical disc drives.
That is, when write enable signals are generated using write strategy data and EFM signals corresponding to respective optical disc manufacturers, the write enable signals may vary for different optical disc drives. Accordingly, even when the same data is written on a plurality of optical discs manufactured by the same manufacturer using a plurality of optical disc drives manufactured by the same manufacturer, deviations may occur between data written on different optical discs.